Your question seems to assume we know what league of legends is. Maybe somebody does, but you're more likely to get help if you could explain specifically what you want to do.

What does "make each champion be a in a .txt file and make the script read from there." mean?

If it means what I think it means, then you could create a file called champions.txt in your mIRC directory and copy/paste all of the lines of text exactly like the one you've just posted into it, then load this script into remotes (Alt+R):

Code:
on *:text:!stats *:#:{
  if ($read(champions.txt,nw,$2- *) != $null) { msg $chan $v1 }
  else { msg $chan Champion $qt($2-) not found. }
}